Nanostructures, including nanotubes, exhibit novel physical properties and play an important role in fundamental research. In addition, nanostructures and nanotubes find many practical applications because of their restricted size and high surface area. See R. Kelsall et al., Nanoscale Science and Technology, Wiley, Chichester, (2006); C. R. Martin, Ace. Chem. Mater. 28, 61 (1995); J. Goldberger et al., Nature, 422 599 (2003); and S. B. Lee et al., Science, 296, 2198 (2002). Nanotubes may be formed from a variety of materials, including different classes of materials such as insulators, semiconductors, and metals, including transition metal oxides. In particular, hafnium oxide (hafnia, HfO2), aluminum oxide (alumina, AlO3), titanium oxide (TiO2) and zirconium oxide (zirconia, ZrO2) are important materials widely used in ceramics, chemical sensors, catalysts, opto-electronics, and as high-k dielectrics in microelectronics. The semiconductor, zinc oxide (ZnO), is also used in chemical sensors. However, a need exists for nanotubes formed from metal oxides and other materials that have more complex structures, higher aspect ratios, and higher surface areas.